1. Field
One or more embodiments relate to a porous anode active material, a method of manufacturing the porous anode active material, an anode including the porous anode active material, and a lithium battery including the anode.
2. Description of the Related Art
In general, graphite, which is a crystalline carbon, is used as an anode active material for lithium ion batteries. Graphite has excellent electrical capacity maintenance characteristics and excellent electrical potential characteristics, and thus is commercially used as an anode active material. However, even though graphite has these good characteristics, it has a low theoretical electrical capacity (hereinafter for simplicity, “electrical capacity” will be referred to as “capacity”). Because of this problem, research is actively underway to find alternatives to graphite. For example, Si, Sn, and Al, which are materials capable of forming an alloy with lithium, can be used as an anode active material.
However, although Si and Sn have higher capacities than graphite, Si and Sn swell when they form an alloy with lithium. Because of the swelling, the active material can become electrically isolated in part inside the electrode. The swelling also leads to an increase in specific surface area that leads in turn to acceleration of the electrolyte decomposition reaction.
To solve these problems, an amorphous Sn-based oxide can be used. For example, the particle size of Sn can be minimized and thereby agglomeration of Sn that occurs when a battery is charged or discharged can be prevented so as to obtain excellent capacity maintenance characteristics.
In another solution to these problems, tin oxide can be formed containing mesopores having a uniform diameter and shape in order to obtain a buffer space in an anode active material so that mechanical deterioration of the anode active material, which may happen during a swelling reaction with lithium, can be decreased (Japanese Patent No. 2002-042808). Use of nanopores may contribute to a decrease in mechanical stress caused by the swelling. However, use of the nanopores can only prevent mechanical stress up to a certain point and beyond this point the nano structure may be mechanically degraded. Therefore, these and/or other problems need to be solved.